This invention relates to a multi-pole circuit interrupter in which a first pole unit with an operating mechanism and a second pole unit without an operating mechanism are provided and in which a movable contact is moved to open by an electromagnetic repulsive force resulting from a large current irrespective of the interrupting operation by an automatic trip mechanism.
A conventional circuit interrupter to which the present invention pertains will be described in conjunction with FIGS. 1 to 8. FIG. 1 is a plan view of a conventional multi-pole circuit interrupter; FIG. 2 is an enlarged cross sectional view taken along line II--II of FIG. 1; FIG. 3 is a partial enlarged sectional view of FIG. 2 showing the ON position; FIG. 4 is a view similar to FIG. 3, but illustrating the OFF position; FIG. 5 is a view similar to FIG. 3, but illustrating the TRIP position; FIG. 6 is a view similar to FIG. 3, but illustrating the electromagnetically operated position; FIG. 7 is an enlarged cross sectional view taken along line VII--VII of FIG. 1 illustrating the on position; and FIG. 8 is an enlarged view of a portion of FIG. 7 but illustrating the off position.
In FIG. 1, the multi-pole circuit interrupter is illustrated as having a housing 1 in which a central, first pole unit 2 provided with an operating mechanism is positioned between a pair of side, second pole units 3 provided with no operating mechanism. The first pole unit 2 has formed therein a window 5 through which an operating handle 4 of the operating mechanism extends.
In FIGS. 2 to 6, which illustrate detailed arrangements of the first pole unit 2 in various operating positions, the electrically insulating housing 1 includes a base 1a and a cover 1b. A stationary source side conductor 6 is mounted on the base 1a and has a stationary contact 7 secured thereon. An automatic trip unit 8 is mounted in the housing 1, and a load side conductor 9 is electrically connected to the automatic trip unit 8. A movable contact 10 is secured to a movable member 11 which is electrically connected to the automatic trip unit 8 through a flexible conductor 12 and a connector 13. The movable member 11 is supported by a contact arm assembly 14 comprising a first contact arm 14a connected to an operating mechanism 23 which will be described in more detail later, and a second contact arm 14b on which the movable member 11 is pivotally supported by a first pin 15. The first contact arms 14a for all of the pole units 2 and 3 are also connected to a cross bar 17 for the simultaneous movement of the pole units 2 and 3. The first contact arm 14a and second contact arm 14b are pivotally supported independently within the housing by a pivot pin 16.
The first contact arm 14a has formed therein a first guide hole 18 extending substantially in a direction of movement of the first contact arm 14a. The guide hole 18 includes a recessed portion 18a in which a sliding pin 20 is received and an end portion 18b against which the sliding pin 20 engages upon the separation of the contacts by electromagnetic repulsion. The guide hole 18 also includes a pin braking portion 180 which is formed in a pin sliding surface 18c along which the sliding pin 20 slides and which is a slanted surface for preventing the bouncing of the sliding pin 20 when it hits the end portion 18b of the guide hole 18.
The second contact arm 14b has formed therein a second elongated guide hole 19 extending in a direction of extension of the second contact arm 14b and in a direction generally perpendicular to the direction of extension of the first guide hole 18. The sliding pin 20 extends through th first and the second guide holes 18 and 19 to limit the relative pivotal movement between the first and second contact arms 14a and 14b. The sliding pin 20 is biased toward the free end of the contact arm 14b by a tension spring 21 mounted between the sliding pin 20 and a pin 15 pivotally connecting the movable member 11 to the second contact arm 14b. In order to provide a contact biasing force between the movable and stationary contacts 10 and 7, a contact pressure spring 22 is disposed between the movable member 11 and the second contact arm 14b. An operating handle 4 is connected to an operating mechanism 23 comprising a releasable cradle 23a having a stop pin 24 and a pair of toggle links 23b and 23c connected between the cradle 23a and the first contact arm 14a by pivot pins 25a and 25b. As is well known, an arc extinguisher 26 is disposed in such a way as to extinguish the arc generated between the separated contacts when they are separated. In FIGS. 7 and 8, which illustrate detailed arrangements of the second pole unit 3 in ON and OFF operating positions, the cover 1b of the housing 1 is integrally provided with a stopper 27 for limiting the movement of the second contact arm 14b.
When the first pole unit 2 with the operating mechanism 23 of the circuit interrupter is in the ON position shown in FIGS. 2 to 3, an electric current flows from the source side stationary conductor 6 to a load side conductor 9 through the stationary contact 7, the movable contact 10, the movable member 11, the flexible conductor 12, the connector 13 and the automatic trip unit 8 in the named order. When the second pole unit 3 without the operating mechanism 23 is in the ON position shown in FIGS. 1 and 7, the electric current flows from the source side stationary conductor 6 to the load side conductor 9 through the stationary contact 7, the movable contact 10, the movable member 11, the flexible conductor 12 and the connector 13 in the named order.
When the operating handle 4 is moved into the OFF position as shown by an arrow 28 of FIG. 3, the contact arm assembly 14 is lifted by the operating mechanism 23 so that the movable contact 10 together with the movable member 11 is moved away from the stationary contact 7 as shown in FIG. 4 to open the contacts 7 and 10. At this time, since the sliding pin 20 is positioned in the recessed portion 18a of the guide hole 18 due to the biasing function of the tension spring 21, the second contact arm 14b is rotated about the pivot pin 16 in the opening direction by the operating mechanism 23 together with the first contact arm 14a until it abuts against the stop pin 24. This movement of the contact arm assembly 14 of the first pole unit 2 with the operating mechanism is transmitted through the cross bar 17 to the second pole unit 3 without the operating mechanism so that the contact arm assembly 14 therein opens until the second contact arm 14b of that pole unit abuts against the stopper 27 mounted on the cover 1b.
In the ON position shown in FIGS. 1 to 3 and 7, when an overload current flows through the circuit interrupter, the automatic trip unit 8 is actuated to release the cradle 23a of the operating mechanism 23 to allow it to rotate in the direction of an arrow 29 of FIG. 3. Then, the toggle links 23b and 23c of the operating mechanism 23 rotate the contact arm assembly 14 in the clockwise direction in the figure to separate the movable contact 10 from the stationary contact 7, thereby interrupting the overload current. This is the so-called tripped position shown in FIG. 5. During this operation, since the sliding pin 20 is positioned within the recessed portion 18a of the guide hole 18 due to the action of the tension spring 21 similarly to the OFF position shown in FIG. 4, the second contact arm 14b is rotated clockwise about the pivot shaft 16 by the operating mechanism 23 together with the first contact arm 14a until it abuts against the stop pin 24. Although not illustrated, the contact arm assembly 14 in the second pole unit 3 is also separated because of the movement of the cross bar 17 until the second contact arm 14b abuts against the stopper 27 on the cover 1b of the housing in a similar manner to that previously described.
When a large current such as a short-circuit current flows through the circuit interrupter in the ON position shown in FIGS. 2 to 3 and 7, an electromagnetic repulsive force generated between the stationary conductor 6 and the movable member 11 causes the movable member 11 to immediately separate from the stationary conductor 6 as shown in FIG. 6. At this time, since the operating mechanism 23 does not allow the first contact arm 14a to be actuated because it has not yet been actuated itself, the second contact arm 14b rotates clockwise about the pivot pin 16 by moving the sliding pin 20 against the spring force of the tension spring 21 from the recessed portion 18a of the guide hole 18 along a pin sliding surface 18c in the guide hole 18 until the sliding pin 20 abuts against an end portion 18b of the guide hole 18 as shown in FIG. 6. Also in the second pole unit 3 in which no operating mechanism is provided, the movable member 11 also moves in the opening direction due to the repulsive force as shown in FIG. 8 until the sliding pin 20 abuts against the end portion 18b of the guide hole 18. In either pole unit 2 or 3, the sliding pin 20 is subjected to a braking force from the pin braking portion 180 of the guide hole 18, so that the sliding pin 20 cannot bounce back at the end portion 18.
An electromagnetic repulsive force is generated very quickly upon the occurence of a short-circuit current and therefore the contact separation is achieved before the automatic trip unit 8 is actuated, providing a high current limiting capability. Immediately after the electromagnetic repulsive separation is achieved, the automatic trip unit 8 trips and rotates the first contact arm 14a to return the sliding pin 20 into the recessed portion 18a along the pin sliding surface 18c of the guide hole 18 after it has passed the position shown in FIG. 6 to take up the tripped position shown in FIG. 5. This is called the resetting of the contact arm assembly 14. At this time since the first contact arm 14a of the contact arm assembly 14 in the second pole unit 3 is tripped through the cross bar 17 and lifted from the repulsion position of FIG. 8, the sliding pin 20 also moves along the pin sliding surface 18c across the pin braking portion 180 until it is received within the recessed portion 18a to take up a tripped position. This repulsive action is quicker than the action of the operating mechanism 23 connected to the movable member 11 through the contact arm assembly 14, thereby increasing the current limiting effect.
With the conventional multi-pole circuit interrupter as above described, the time points at which the sliding pins 20 of respective pole units 2 and 3 move over the corresponding pin braking portions 180 of the respective guide holes 18 during the resetting of the first contact arms 14a are concurrent to each other, requiring a large force to reset the first contact arms 14a so that the operating mechanism 23 must be made large-sized.